Method of making bone black



y 1932- T. L. WHEELER ET AL 1,856,302

METHOD OF MAKING BONE BLACK Filed April 11, 1929 .li werauifarisj7e0M/lrLaII/llt 117 W612 e?" vii 1; W15 ME til Patented May 3, 1932 UNITED STATES PATENT OFFICE THORNE IA- WHEELER, OF GHATI-IAM, NEW YORK, AND JOHN B. CARPENTER, JR., OF

WEST ROXBURY, MASSACHUSETTS, ASSIGNORS TO ARTHUR D. LITTLE, INCORPO- RATED, OF CAMBRIDGE, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS METHOD OF MAKING BONE BLACK Application filed April 11,

This invention relates to the manufacture of bone black from bones.

According to present practice ground or cracked bones are charred by maintaining them in a retort at a temperature of 1000 to 1300 Fahr. for from nine to twelve hours. Apparatus commonly employed for this purpose consists of tubular retorts of relatively great length as compared to their diameter set vertically in a furnace. Each retort is provided with a charge gate at the top and a discharge gate at the bottom and also with vents at the top for the escape of volatile matter, these parts of the retort being outside of the brick work of the furnace. The operation is on the batch principle. The retort is filled, or nearly filled, with ground or cracked bones introduced through the charge opening at the top. The charge gate is then closed. The charring operation is continued for from nine to twelve hours at temperatures of the order above stated depending on the type of bones charged and the quality of black desired. The volatile matter which comes off through the vents at the top of the retort during the charring operation is collected and further treated for the recovery of such by-products as ammonia, tar and fixed gas. Upon the completion of the charring operation the bone black is discharged through the discharge gate at the bottom into drums. Although minor variations from the practice just outlined may occur. the operation described is in all essential respects typical of current procedure. This operation is slow; it requires much labor and the quality of the bone black produced is not regular and uniform due to the difficulty of getting a uniform heat distribution on the outside of the retort and the poor conductivity of the bones or bone black.

Our new process is a continuous process as distinguished from a batch process and is a relatively brief two-stage process as compared to a long one-stage process. Briefly stated, the process comprises subjecting the ground or cracked bones uniformlv to heat of suihcient degree to char or partially char the bones and to drive off the vapor part of the low boiling volatile matter. This can be 1929. Serial No. 354,330.

accomplished at a temperature of from 900 to 1300 Fahr. in a period of from one hour to two hours, during which period most of the volatile matter is driven out. This is preferably carried on in an externally fired rotary retort which by its movement exposes all the particles of the charge to the same heat conditions and at the same time feeds the material through the heating zone. The material produced by said first stage is then heated to from 1500 to 2000 Fahr. for a very short period, say from five to fifteen minutes, to complete the carbonizing of the material and to eliminate the high boiling point tars, etc.,- which are either driven off or charred in a more effective manner than is accomplished by the heating at lower temperatures for a period of several hours according to previous practice. The second or brief high temperature stage is also preferably performed in an externally fired rotary retort similar to that used in the first stage.

Although the practice of the invention is not restricted to the use of any particular apparatus, We will by way of illustration describe it in detail in connection with an apparatus capable of being used advantageously in the practice of the invention. Such apparatus is shown in the accompanying drawing in diagrammatic, sectional elevation.

The ground or cracked bones to be treated are placed in a charging hopper 1 which is connected by a pipe or chute 2 to the housing 4. The feed of the materials into the housing 4 is by gravity and the rate of feed may be controlled by a cook or gate 3. The bottom floor 4 of the housing4 is preferably inclined to deflect the incoming charge into the rotary retort 5.

It will be understood that the particular kind of charging apparatus is not essential to the present invention. Any suitable form of charging mechan sm may be used, such as a belt conveyor or a screw convevor or other form of feeding device familiar to one skilled in the art.

The first step of the process, which comprises a relatively slow carbonizing of the material at a relatively low temperature, that is, a temperature of the order heretofore used for the entire process, is performed in the rotary retort 5. The rotary retort 5, while slightly inclined, is of the horizontal type and consists of a long steel drum or cylinder provided with ring tracks or flanges 6 which rest on suitable roller bearings 7. The entrance end of the retort 5 communicates with the housing 4 and the delivery end of the retort communicates with the housing 8. The junctions of the drum with the housings 4 and 8 are preferably provided with gas tight joints, not shown. The drum is provided with a ring gear 9 which meshes with a pinion 10 on shaft 11 to which power is applied from any suitable source for rotating the drum. The axis of the retort 5 is preferably inclined, slightly downward, from the entrance end to the discharge end in order to feed the materials slowly through the drum as the latter rotates. The entrance end of the retort is also preferably provided with a series of flights 12 on the interior surface to facilitate picking up the materials delivered to the retort from the housing and starting them on their progress through the retort.

The retort 5 is heated externally as by burners for gas or any suitable commercial fuel in a furnace or combustion chamber enclosed by furnace walls 13, all properly designed for maintaining a regulated and even temperature throughout that part of the drum enclosed by the furnace Walls.

The length of the retort 5, its diameter, the inclination of the axis, its speed of rotation and the rate of delivery of the ground bones into the retort are so coordinated as to heat the charge passing through the heat zone enclosed by the furnace walls 13 for a period of from one to two hours; and the temperature maintained during this heat treatment is preferably from 900 to 1300 Fahr. During this heat treatment most of the volatile matter is driven off and is removed from the retort througha flue 30 in the top of housing 4. If necessary or desired, another flue 14: maybe provided on housing 8 to act in conjunction with flue 30. Flue 14 is preferably equipped with a valve 14' by which the fine 14 may be cut off ifit is desired to withdraw all the gases through flue'30. Flues 30 and 14 may be connected with suitable condensing and absorption equipment, not shown, but familiar to one skilled in the art, for recovering the by-products as usual from the volatilized material driven off in the retort 5, such as ammonia, tar and fixed gas.

Located preferably below the retort 5, so that the material may be delivered thereto by gravity, is a second rotary retort 18 of the horizontal type consisting of a heat-resisting metal cylinder or drum whose ends extend into housings 17 and 19, the junctions with the housings being preferably provided with suitable gas tight joints (not shown). The

hot charred material delivered from the first rotary retort 5 into the housing 8 is conveyed through a conduit or chute 15 into the housing 17, the rate of flow being controlled by a gate or valve 16. The retort 18, like the retort 5, is mounted for rotation on roller bearings 7 and is driven from any suitable source of power by means of shaft 20, pinion 21 and ring gear 22 similar in construction to the corresponding parts on retort 5.

The retort 18 is heated externally by burners adapted for gas or any suitable commercial fuel within the furnace walls 23, these parts being organized to maintain an even temperature throughout that section of the retort enclosed within the furnace setting 23.

The axis of the retort 18 is inclined so as to feed the materials from the entrance end to the delivery end of the retort. The discharge hopper 19 at the delivery end of the retort communicates with a discharge conduit 24 by which the carbon material is removed from the hop-per 19, the rate of discharge be. g regulated by any suitable valve mechanism 24 adapted to prevent air from entering the retort thereby preventing combustion within the retort.

Conduit 24 communicates with a cooler, not shown, but which may be of any suitable type known to those skilled in the art whereby the hot material may be cooled in such manner. as to prevent air from coming in contact with the hot material, thus preventing combustion within the cooler.

The temperature in the heating zone of retort 18 is preferably maintained at 1500 to 2000 Fahr. and the length of the heat zone, the diameter of the retort, the inclination of the axis of the retort, its speed of rotation and the rate of delivery of carbon materials into the retort are so related as to heat the material passing through the heating zone for a relatively short period of time, say from five contents or part of the contents of housing 8 through conduit 25 into a receptacle 26. Receptacle 26 is connected by a conduit or chute 27 to housing 17, a valve or gate 28 being provided in conduit 27 to regulate the rate of flow.

If desired, materials treated in retort 5, or part of such materials, may be delivered into the auxiliary receptacle 26, or material other than that carbonized in retort 5 may be stored in auxiliary receptacle 26, and the contents of receptacle 26 may be drawn upon in place of or to supplement materials flowing directly from retort 5 for charging retort 18.

Any volatilized material resulting from the further distillation of the material in retort 18 may be removed from the retort through a vapor pipe or fine 29 at the top of housing 19 and conveyed to the condensing and absorption equipment already mentioned.

its will he understood from the foregoing. after the apparatus is once started the various mechanisms controlling the rate of teed and discharge to and from the various drums and containers may be so regulated that there will be a continuous flow of material through the entire apparatus.

Advantages of the new process are that it is a continuous process instead of a batch process; that it produces a better and more uniform quality of product; that it reduces the time of chairing, the amount of labor and the consumption of fuel as compared to processes now in current use, thus lowering the cost of operation; and that by delivering the finished material continuously at one point instead of from a large number of individual retorts, it facilitatestransferring the material to a suitable cooler without contact with air.

Without attempting to state What if any physical or chemical changes in the absorp tive carbon itself result from the high temperature step. apart from the elimination of the high boiling volatiles, we find that bone black made b v our process is better and more active as a decolorizing agent than bone black made by previous processes involving a single heat treatment of long duration at relatively low temperatures. Our high temperature step may be used with marked advantage tor the further treatment of bone black as ordinarily produced by previous processes.

We claim:

l. The method of making bone black from bones which comprises heating the bones at a temperature of from 900 to 1300 Fahr. tor a period of from one to two hours and thereafter heating the resulting material at a substantially higher temperature for a relativelv short time.

2. The method of making hone black from bones which comprises heating thevbones at a temperature of from 900 to 1300 Fahr. :tor a period of from one .to two hours and thereafter heating the resulting material at a temperature of from 1500 to 2000 Fahr. for from five to fifteen minutes.

3. The method of making bone black from bones which comprises continuously passing a stream of ground or cracked bones through a heat treatment at a temperature of from 000 to 1300 Fahr. for a period of from one to two hours in a rotating retort and thence through a heat treatment at a temperature of from 1500 to 2000 Fahr. for a eriod of from five to fifteen minutes in a rotating retort.

i. That step in the method of making bone black which comprises subjecting previously charred bones immediately to a temperature of atleast 1500 Fahr. for a suflicient length of time to substantially eliminate high boiling volatile matter.

5. That step in the method of making bone black which comprises subjecting previously charred bones to a temperature of from 1500 to 2000 Fahr. for from five to fifteen minutes.

6. That step in the method of making bone black which comprises subjecting previously charred bones immediately to a tempera ture of at least 1500Fahr. in a rotating retort for a sufiicient length of time to substantially eliminate high boiling volatile matter.

' 7. That step in the method of making bone black which comprises subjecting previously charred bones to a temperature of from 1500 to 2000 Fahr. in a rotating retort for from five to fifteen minutes.

Signed by us at Cambridge, Mass, this 9th day of April, 1929.

THORNE L. WHEELER. JOHN B. CARPENTER, JR. 

